Study designs are placed into a hierarchy based on their reliability (probability of bias) known as the Levels of Evidence.
The Levels of Evidence are often represented by a pyramid, with the highest levels of evidence (least common) near the top, and the lowest levels of evidence (most common) near the bottom. The pyramid above is based on the Oxford Centre for Evidence Based Medicine's rating system for therapeutic studies, but a variety of rating systems exist.
Use this worksheet to break down the parts of your PICO question.
Question Type & Study Design
Some study designs are better suited to answer certain types of questions. Identifying the clinical domain your question falls under can help determine what study designs to look for in order to find the best, most suitable evidence. Systematic Reviews and Meta-Analyses are always preferred.
Check off the clinical domain and preferred study design type on the Well-Built, Patient-Oriented Clinical Question worksheet. The link to that worksheet can be found above.
Preferred Study Design (after systematic reviews and meta-analyses)
Randomized Controlled Trial > Controlled Trial or Quasi-Experimental Studies
Clinical question: In adult patients with total hip replacements, how effective is pain medication compared to aerobic stretching in controlling post operative pain during the perioperative and recovery time?
Clinical domain: Therapy
Preferred study designs: Systematic Reviews, Meta-Analyses, Randomized Controlled Trials, and Controlled Trials